Disk array optimizing the drive operation time

ABSTRACT

In accordance with one embodiment of the invention, a storage system is configured as at least one logical unit including at least one disk device; a controller for executing a read processing or a write processing of data having been stored or to be stored in the logical unit which is a destination of a read request or a write request, in response to the read request or write request transmitted from the computer, wherein the controller receives an instruction from the computer to turn on or off a disk device corresponding to the logical unit; and wherein, based on the instruction, the storage system turns on or off the disk device corresponding to the logical unit independently of disk devices corresponding to the other logical units.

CROSS REFERENCE TO RELATED APPLICATION(S)

This is a continuation of U.S. patent application Ser. No. 10/777,832,filed Feb. 11, 2004, which application claims priority from Japan PatentApplication No. 2003-394919, filed Nov. 26, 2003, the entire disclosureof which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to an external storage device system. Morespecifically, the present invention relates to a technology forprolonging an operation period of a disk device (hereafter also referredto simply as a disk) and decreasing power consumption of a storagedevice system (hereafter referred to as a disk array). Here, the diskdevice's operation period signifies a period from the time to startusing the disk device to the time when the disk device becomes unusable.

A disk array is a type of storage device systems connected to acomputer. The disk array is also referred to as a RAID (Redundant Arraysof Inexpensive Disks) and constitutes a storage device system comprisinga plurality of disk devices arranged in an array and a control sectionto control them. The disk array concurrently operates disk devices toaccelerate read requests (requests to read data) and write requests(requests to write data) and to provide data with redundancy. Diskarrays are categorized into five levels depending on types of redundantdata to be added and disk array configurations. This is described innon-patent document 1 (Daved A. Patterson, Garth Gibson, and Randy H.Katz, “A Case for Redundant Arrays of Inexpensive Disks (RAID)”,Computer Science Division Department of Electrical Engineering andComputer Sciences, University of California Berkeley, 1988).

SUMMARY OF THE INVENTION

Some disk devices used for a disk array may shorten a total active timewhen they are turned on 24 hours a day in comparison to a case where thedisk devices are turned on only when needed. The total active timesignifies the accumulated time during which the disk device is turnedon. Such problem caused by deterioration and wear of parts constitutingthe disk devices. The disk device's total active time shortens when thedisk device is turned on 24 hours a day and is operated continuously 24hours a day. As a result, the disk device's operation period shortens.Such disk device is not suited for 24-hour continuous operations. Thedisk array capacity increases year after year. There is a trend ofincreasing the number of disk devices to be mounted. The powerconsumption for disk arrays tends to increase.

The present invention discloses a technology to prolong operation timesof disk devices constituting a disk array. The present invention alsodiscloses a technology to decrease the disk array's power consumption.

A computer accessing a disk array has a disk control instruction programwhich allows the disk array to turn on or off specific disk devices init. The disk array has a disk power supply control instruction receptionprogram and a disk power supply control circuit. The disk power supplycontrol instruction reception program receives an instruction to turn onor off disk devices from the computer. The disk power supply controlcircuit turns on or off a disk device corresponding to an LU specifiedby the computer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a system configuration according to a firstembodiment;

FIG. 2 shows an example of a computer configuration according to thefirst embodiment;

FIG. 3 shows an example of a backup server configuration according tothe first embodiment;

FIG. 4 shows an example of a disk management table according to thefirst embodiment;

FIG. 5 shows an example of an update position management table accordingto the first embodiment;

FIG. 6 shows an example of obtaining or deleting a snapshot according tothe first embodiment;

FIG. 7 shows a process example of a mirror resynchronization programaccording to the first embodiment;

FIG. 8 shows an example of a system configuration according to a secondembodiment;

FIG. 9 shows an example of a computer configuration according to thesecond embodiment;

FIG. 10 shows an example of an address map according to the secondembodiment; and

FIG. 11 shows a process example of a disk power supply controlinstruction program according to the second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described in further detailwith reference to the accompanying drawings.

First Embodiment

The first embodiment will now be described.

(1) Description of the System Configuration

FIG. 1 shows an example of the system configuration according to thefirst embodiment. In FIG. 1, a computer 100 is connected to a disk array200 via a Fibre Channel interface (hereafter referred to as an FC I/F)290 of the disk array 200. A backup server 400 is connected to the diskarray 200 via an FC I/F 300 of the disk array 200. A tape apparatus 500is connected to the backup server 400. A management terminal 600 isconnected to the disk array 200 via a management I/F 310 of the diskarray 200.

The disk array 200 comprises a CPU 210, memory 220, a cache 240, and adisk controller 250. The CPU 210 controls the disk array 200. The cache240 stores user data of the disk array 200. The disk controller 250controls a plurality of disk devices.

The disk controller 250 is connected to a plurality of FC disks 271through 273 (hereafter referred to as an FC disk group) and a pluralityof ATA disks 274 through 276 (hereafter referred to as an ATA diskgroup). The FC disk group and the ATA disk group each use a redundantconfiguration called RAID. The computer 100 accesses storage areas inthe FC disks 271 through 273 as a SCSI logical unit (LU). Likewise, thecomputer 100 also accesses storage areas in the ATA disks 274 through276 as a SCSI LU. An LU 261 represents the LU in the FC disks 271through 273. An LU 262 represents the LU in the ATA disks 274 through276. FIG. 1 illustrates the LU 261 and the LU 262 each as a storage areacovering a plurality of disks. Further, the LU may comprise a storagearea on one disk.

According to the embodiment, the snapshot management program 226 in thedisk array 200 manages the LU 261 and the LU 262 duplicatively. Whendata is written to the LU 261 according to the embodiment, the snapshotmanagement program 226 writes the same data to the LU 262 to duplicatethe data. In this manner, storing the same data in the LU 261 and the LU262 is referred to as mirroring data. The LU 261 contains original dataand is referred to as a mirror origin LU. The LU 262 contains a copy ofthe original data and is referred to as a mirror destination LU. The LU262 is used to obtain a snapshot. The snapshot is used to back up dataon the tape apparatus.

A disk power supply control circuit 280 is connected to the ATA disks274 through 276. The disk power supply control circuit 280 turns on oroff each ATA disk independently of the other ATA disks. The disk powersupply control circuit 280 is provided with registers corresponding tothe ATA disks 274 through 276. Turning on or off the register turns onor off the corresponding ATA disk.

The following describes programs and management tables in the disk array200.

The memory 220 of the disk array 200 contains a RAID control program221, a disk management program 222, a disk power supply controlinstruction reception program 223, a disk management table 224, a diskpower supply control program 225, and a snapshot management program 226.The RAID control program 221 controls the disk array 200. The diskmanagement program 222 manages the FC disks 271 through 273 and the ATAdisks 274 through 276. The disk management table 224 records operationparameters and operation states of the FC disks 271 through 273 and theATA disks 274 through 276. The disk power supply control instructionreception program 223 receives an instruction to turn on or off diskdevices from the computer 100. This instruction is hereafter referred toas a disk power supply control instruction. The disk power supplycontrol program 225 turns on or off the ATA disks 274 through 276 basedon instructions received from the computer 100. The snapshot managementprogram 226 controls snapshots. According to the embodiment, a snapshotinstruction program 127 to be described is contained in the computer 100and issues instructions to delete or obtain snapshots. In addition, thesnapshot instruction program 127 issues ModeSelect commands concerningdisk power supply control instructions for the ATA disks 274 through276. Accordingly, the snapshot management program 226 accepts not onlyinstructions to delete or obtain snapshots, but also disk power supplycontrol instructions for the ATA disks 274 through 276.

The snapshot management program 226 also contains a disk accesssub-program 227 and an LU mirror sub-program 228. The disk accesssub-program 227 instructs the disk controller 250 to access disks inaccordance with requests from the computer 100. The LU mirrorsub-program 228 applies an update to one LU and another predetermined LUand writes the same user data to two LUs. The LU mirror sub-program 228duplicates data written to the LU 261 for the LU 262.

The snapshot management program 226 further contains a non-mirror updatemonitoring sub-program 230, a non-mirror update position managementsub-program 231, and a mirror resynchronization sub-program 229. Whenthe data duplication is inactivated between the LU 261 and the LU 262(non-mirror state), the non-mirror update monitoring sub-program 230detects an update to the mirror origin LU. The non-mirror updateposition management sub-program 231 records the update position in anupdate position management table 232 to be described later. When themirror resynchronization is performed to restart data duplicationbetween the LU 261 and the LU 262, the mirror resynchronizationsub-program 229 copies the updated part of the mirror origin LU to themirror destination LU.

The update position management table 232 is used to manage the contentsof data stored in the mirror origin LU and the mirror destination LU.When data in the mirror origin LU is updated in the non-mirror mode, theupdate position management table 232 records the update position in themirror origin LU.

For example, the update position management table 232 is a bit map asshown in FIG. 5 and lists LBA set numbers in the mirror origin LU andupdate bit states corresponding to the LBA set numbers. Each LBA setcomprises one, or the same number of LBAs (Logical Block Addresses) thatare used as a unit to divide the entire area in the LU from thebeginning. The LBA sets are assigned LBA set numbers, i.e., sequencenumbers, from the beginning.

The update bit indicates whether or not the LBA set corresponding to theupdate bit is updated in the non-mirror mode. The update bit is set to 1when the LBA set is updated, or to 0 otherwise. The update bit isinitially set to 0. For example, the update position management table232 in FIG. 5 shows that only the area corresponding to LBA set number 1is updated in the non-mirror mode.

Referring now to FIG. 4, an example of the disk management table 224will now be described. The disk management table 224 comprises thefollowing columns. The “disk No.” column shows identification numbers ofdisk devices in the disk array 200. The “disk type” column shows thedisk type, i.e., whether the disk device is an FC disk or an ATA disk.The “array configuration” column shows to which RAID group the diskdevice belongs. The “LU No.” column shows to which LU the disk devicebelongs. The “snapshot pair” column shows whether data stored in thedisk is original or copy. The “snapshot status” column shows whether ornot data to be stored in an FC disk is mirrored to an ATA disk. The“disk startup status” column shows whether the disk device is turned onor off. The “accumulated time” column shows the accumulated time inwhich the disk device is turned on. The “life setting” column shows thelimit of the accumulated time in which the disk device is turned on.

Returning now to FIG. 1, the management terminal 600 comprises an inputsection 610 and an output section 620. The input section 610 acceptssettings for the FC disks 271 through 273 and the ATA disks 274 through276 from a user. The output section 620 displays information about theFC disks 271 through 273 and the ATA disks 274 through 276 to the user.

The input section 610 inputs parameters to be assigned to the diskmanagement table 224. The output section 620 outputs informationrecorded in the disk management table 224. The input section 610represents a mouse, a keyboard, and the like. The output section 620represents a display, an liquid crystal panel, a buzzer, and the like.

Referring now to FIG. 2, an example of the computer 100 will now bedescribed. The computer 100 comprises a CPU 110, an FC I/F 140, acommunication I/F 160, and memory 120. The CPU 110 controls the computer100. The I/F 140 connects the computer 100 to the disk array 200. Thecommunication I/F 160 provides communication between the computer 100and the backup server 400. The memory 120 stores programs.

The memory 120 stores a database program 126, a snapshot instructionprogram 127, and a disk power supply control instruction program 128.The snapshot instruction program 127 allows the disk array 200 to obtainsnapshots. The disk power supply control instruction program 128instructs to turn on or off disk devices in the disk array 200. The CPU110 to control the computer 100 executes these programs. The snapshotinstruction program 127 generates and issues SCSI ModeSelect commands.The ModeSelect commands include an instruction to turn on or off the ATAdisks 274 through 276 from the disk power supply control instructionprogram 128 to the disk array 200. The ModeSelect commands also includean instruction to delete or obtain snapshots from the snapshotinstruction program 127 to the disk array 200. The database program 126accesses the LU 261, i.e., the mirror origin LU while the database isreferenced or updated. The database program 126 also controls dataupdate. The database program 126 stops accessing the disk array 200 at acheck point that indicates a meaningful separation as databaseinformation. When data in the LU 261 becomes meaningful as databaseinformation, the database program 126 changes the disk array to a backupmode to back up that data. The backup mode ensures the consistency ofdata in the LU 261.

Referring now to FIG. 3, an example of the backup server 400 will now bedescribed. The backup server 400 comprises a CPU 410, an FC I/F 440, acommunication I/F 460, a SCSI I/F 450, and memory 420. The CPU 410controls the backup server 400. The FC I/F 440 connects the backupserver 400 with the disk array 200. The communication interface 460provides communication between the backup server 400 and the computer100. The SCSI I/F 450 connects the backup server 400 with the tapeapparatus. The memory 420 stores programs. The memory 420 stores abackup program 426, an I/O control program 427, and a tape controlprogram 428. The backup program 426 backs up data in the disk array 200onto the tape apparatus 500. The I/O control program 427 transfers databetween the disk array 200 and the tape apparatus 500. The tape controlprogram 428 control the tape apparatus 500. The CPU 410 to control thebackup server 400 executes these programs.

There has been described the system configuration of the embodiment.

(2) Obtaining and Deleting Snapshots

With reference to the flowchart in FIG. 6, the following describes anexample of processes performed by the snapshot instruction program 127and the snapshot management program 226 when snapshots are obtained ordeleted. The embodiment assumes that the disk array 200 obtains asnapshot of the LU 261 in synchronization with the timing when thebackup server 400 backs up data. It also assumes to turn on the ATAdisks 274 through 276 for the LU 262 only during a period in which asnapshot is obtained and data is backed up from mirror destination LU.

Since the LU 262 stores data of the previously obtained snapshot, thesnapshot instruction program 127 running on the computer 100 needs tonullify that snapshot and obtain a new snapshot. Hereafter, this isreferred to as deletion of the snapshot. For this purpose, the snapshotinstruction program 127 issues a ModeSelect command to the disk array200 to delete the snapshot (step 2001).

The snapshot management program 226 in the disk array 200 receives theModeSelect command (step 3001). Based on the disk power supply controlinstruction included in the ModeSelect command, the snapshot managementprogram 226 turns on the ATA disks 274 through 276 (step 3002). The diskpower supply control instruction turns on the disk devices correspondingto the LU 262. According to the instruction, the disk array 200 locatesATA disks constituting the LU 262 from the disk management table 224 inFIG. 4 and turns on the ATA disks 274 through 276 in this embodiment.The LU mirror sub-program 228 is activated to restart duplication of theLU 261 and the LU 262 (step 3003). In this embodiment, the activationmeans starting or initiating a process or a program. The inactivationmeans terminating or stopping a process or a program. At step 3003, theLU 262 reflects the update to the LU 261.

The snapshot management program 226 inactivates the non-mirror updatemonitoring sub-program 230 and the non-mirror update position managementsub-program 231 to stop recording updates to the LU 261 (step 3004).Thereafter, the update bit in the update position management table 232is not changed by the non-mirror update position management sub-program231.

The snapshot management program 226 then activates the mirrorresynchronization sub-program 229. The mirror resynchronizationsub-program 229 references the update position management table 232.When the LU 261 contains data that differs from data stored in the LU262, the mirror resynchronization sub-program 229 copies that data fromthe LU 261 to the LU 262 to resume the mirror state between the LU 261and LU 262 (step 3005). This is also referred to as resynchronization.

Upon completion of the resynchronization, the snapshot managementprogram 226 inactivates the mirror resynchronization sub-program 229(step 3006). The snapshot management program 226 sends the terminationstatus of the ModeSelect command to the snapshot instruction program 127on the computer 100 (step 3007). The snapshot instruction program 127receives the termination status of the ModeSelect command to terminatethe operation (step 2002).

The snapshot instruction program 127 on the computer 100 then issues aModeSelect command to obtain a snapshot on the disk array 200 (step2003).

The snapshot management program 226 on the disk array 200 receives theModeSelect (step 3008). The snapshot management program 226 activatesthe non-mirror update monitoring sub-program 230 and the non-mirrorupdate position management sub-program 231 to allow the update positionmanagement table 232 to record the position information about the dataupdate applied to the LU 261 (step 3009). That is to say, when the LU261 is updated, the update position management table 232 indicates theupdate bit set to 1 for the LBA set including the updated LBA to recordthe update.

The snapshot management program 226 then inactivates the LU mirrorsub-program 228 to stop duplication of the LU 261 and the LU 262 (step3010). This prevents the LU 262 as the mirror destination LU fromreflecting the update to the LU 261 as the mirror origin LU.

The snapshot management program 226 then sends the termination status ofthe ModeSelect command to the snapshot instruction program 127 on thecomputer 100 (step 3011).

The snapshot instruction program 127 on the computer 100 receives thetermination status of the ModeSelect command from the snapshotmanagement program 226 (step 2004). The snapshot instruction program 127supplies the backup server 400 with an instruction to obtain a backupvia the communication I/F 160. The backup server 400 receives thetermination report (step 2005). The snapshot instruction program 127then issues a ModeSelect command to turn off the ATA disks 274 through276 to the snapshot management program 226 (step 2006). The procedure toturn off the ATA disks 274 through 276 is the same as that at step 3002.

When receiving the ModeSelect command, the snapshot management program226 in the disk array 200 turns off the ATA disks 274 through 276according to the disk power supply control instruction contained in theModeSelect command (step 3012).

There have been described the operations of the snapshot instructionprogram 127 and the snapshot management program 226 when snapshots areobtained or deleted.

(3) Write Operation

The following describes a write operation of the RAID control program221 in the disk array 200. When the computer 100 writes data to the LU261 to update the contents stored in the LU 261, the snapshot managementprogram 226 receives a WRITE command and data issued to the LU 261.

Let us assume that the LU mirror sub-program 231 is active and that thenon-mirror update monitoring sub-program 230 and the non-mirror updateposition management sub-program 231 are inactive. When receiving writedata from the computer 100, the snapshot management program 226 writesthe write data to both the LU 261 as the mirror origin LU and the LU 262as the mirror destination LU.

Let us assume that the LU mirror sub-program 231 is inactive and thenon-mirror update monitoring sub-program 230 and the non-mirror updateposition management sub-program are active. In this case, the snapshotmanagement program 226 writes data to the LU 261 as the mirror originLU. While the update position management table 232 records updatepositions, the snapshot management program 226 allows this table to setthe update bit to 1 for the LBA set including the updated LBA.

Finally, the status is sent to the computer 100.

(4) Mirror Resynchronization

The following describes an example of the mirror resynchronization tocopy data from the LU 261 to the LU 262 at step 3003 in FIG. 6. FIG. 7exemplifies an operation of the mirror resynchronization sub-program 229during mirror resynchronization. The mirror resynchronizationsub-program 229 checks whether or not the update position managementtable 232 contains the update bit set to 1 to record the update (step1001). When there is no update bit set to 1 to record the update, themirror resynchronization is complete. The mirror resynchronizationsub-program 229 terminates the process (step 1002).

When there is an update record, the mirror resynchronization sub-program229 references the update position management table 232. Based on theLBA set number corresponding to the update bit set to 1, the mirrorresynchronization sub-program 229 calculates a read position on the LU261 and a write position on the LU 262 (step 1003).

The mirror resynchronization sub-program 229 prevents data from beingupdated to the corresponding read/write position (step 1004). Based onthe calculated read/write position, the mirror resynchronizationsub-program 229 copies the data stored at the read position in the LU261 as the mirror origin LU to the write position in the LU 262 as themirror destination LU (step 1005). It should be noted that preventingthe update is equivalent to inhibiting writing. The update is preventedto ensure the consistency of data between the LU 261 and the LU 262after the mirror resynchronization.

The mirror resynchronization sub-program 229 then releases theprevention against updating data at the corresponding read/writeposition (step 1006). The mirror resynchronization sub-program 229 sets0 to the update bit in the update position management table 232correspondingly to the mirrored position due to the copy at step 1005(step 1007), and then returns to step 1001.

There has been described the mirror resynchronization.

(5) Disk Operation Time Management

Using the input section 610 of the management terminal 600, a user canset the life of each of the FC disks 271 through 273 and the ATA disks274 through 276 in the disk management table 224. The life signifies aproduct cycle estimated from the disk design specifications of the diskdevice, or a warranty period, or an accumulated operation time overwhich the disk is highly possibly subject to errors. It is assumed tofind an accumulated time by totaling the time during which the diskdevice is turned on. When the accumulated time exceeds the life, thereis a high possibility of causing an error.

The disk management program 222 records the disk device's accumulatedtime in the disk management table 224. The disk management program 222counts the time during which the FC disks 271 through 273 and the ATAdisks 274 through 276 are turned on. The disk management program 222records the counted time as the accumulated time in the disk managementtable 224. The disk management program 222 compares the life of each ofthe FC disks 271 through 273 and the ATA disks 274 through 276 with theaccumulated time. When the accumulated time exceeds the life, the diskmanagement program 222 displays an alarm on the output section 620 ofthe management terminal 600.

According to the first embodiment as mentioned above, the snapshotmanagement program obtains a snapshot of the LU 262 in synchronizationwith the timing when the backup server obtains a backup. It is possibleto turn on the ATA disk device storing the snapshot data only when thesnapshot management program obtains a snapshot and backs it up on thetape. In other words, the disk device can be turned off while no backupis created. This can extend the operation period of disk devices in thedisk array 200 and decrease the power consumption of the disk array 200.

The disk array 200 receives the ModeSelect command issued from thecomputer 100. At this time, the disk controller 250 controls turning onor off the disk device. While the disk device is turned off, thecomputer 200 does not access the disk device. This can prevent atime-out condition of access requests from the computer 200.

Second Embodiment

The second embodiment will now be described.

(1) Description of the System Configuration

FIG. 8 shows an example of the system configuration according to thesecond embodiment. The following describes only differences from thefirst embodiment. Unlike the example in FIG. 1, the system in FIG. 8uses entirely ATA disks 281 through 289 connected to the disk controller250. The computer 100 accesses a storage area in the ATA disks 281through 283 as a SCSI LU. Likewise, the computer 100 accesses a storagearea in the ATA disks 284 through 286 as another SCSI LU. The computer100 accesses a storage area in the ATA disks 287 through 289 as yetanother SCSI LU. The LU in the ATA disks 281 through 283 is defined asan LU 263. The LU in the ATA disks 284 through 286 is defined as an LU264. The LU in the ATA disks 287 through 289 is defined as an LU 265.FIG. 8 shows that each of the LU 263, the LU 264, and the LU 265constitutes a storage area extending to a plurality of disks. Each LUmay comprise a storage area in one disk. According to an instructionfrom the disk power supply control program 225, the disk power supplycontrol circuit 280 turns on or off the ATA disks 281 through 289independently of the other ATA disks.

The memory 220 stores an LU protection program 234 that protects the LUsagainst reading or writing instead of the snapshot management program226.

Unlike the example in FIG. 4, the disk management table 224 according tothe second embodiment does not record the snapshot pair or the snapshotstatus.

FIG. 9 shows an example of the computer 100 according to the secondembodiment. Unlike the example in FIG. 2, the computer 100 contains anE-mail application program 130, an LU protection instruction program131, and a disk power supply control instruction information storagearea 132 instead of the database program 126 and the snapshotinstruction program 127. The LU protection instruction program 131instructs protection against reading or writing to the LUs. The E-mailapplication stores electronic mail archives in the memory 120,sequentially writes data, and stores data at consecutive addresses. Thisembodiment will be described using the E-mail application as an example.The E-mail application specifies a sequence of LUs to be written.According to the embodiment, the E-mail application accesses the LU 263,LU 264, and LU 265 in this order at scheduled times to write data. Theembodiment is not limited to the E-mail application.

The disk power supply control instruction information storage area 132stores an address map as shown in FIG. 10. The address map lists LUnumbers, LBA numbers, and disk startup status of disk devicesconstituting LUs. The disk startup status provides information aboutpower-on/off states of the disk devices.

The computer further contains a management I/F 150 that is connected tothe management terminal 600.

There has been described the system configuration according to thesecond embodiment.

(2) Operation of the Disk Power Supply Control Instruction Program

The E-mail application 130 issues a request to write data to the diskarray 200 for sequential access. Based on this request, the disk powersupply control instruction program 128 in the computer 100 referencesthe address map in FIG. 10. The disk power supply control instructionprogram 128 issues an instruction to turn on disk devices belonging tothe LU corresponding to the address for writing. The disk power supplycontrol instruction program 128 issues an instruction to turn off diskdevices belonging to the LU corresponding to the address for which thewriting is complete. When reading data, a user uses the input section610 of the management terminal 600 to issue an instruction to turn ondisk devices belonging to the LU that stores data to be read.

FIG. 11 is a flowchart showing an operation example of the disk powersupply control instruction program 128 in the E-mail application. Let usassume that the E-mail application 130 makes preparations for writing tothe LU 263. Based on an request from the E-mail application 130 to writeto the disk array 200, the disk power supply control instruction program128 instructs the disk array 200 to turn on the disks constituting theLU 263 (step 5001). The E-mail application 130 starts writing to the LU263. The disk power supply control instruction program 128 thendetermines whether or not the remaining time is shorter than or equal tothe specified time until the scheduled time of terminating the access tothe LU 263 (step 5002). When the remaining time is longer than thespecified time until the scheduled time of terminating the access, thedisk power supply control instruction program 128 repeats thedetermination at step 5002. When the remaining time becomes shorter thanthe specified time, the disk power supply control instruction program128 instructs the disk array 200 to turn on the LU 264 (step 5003). Thedisk power supply control instruction program 128 then determineswhether or not the E-mail application 130 starts accessing the LU 264(step 5004). When the E-mail application 130 does not start accessingthe LU 264, the disk power supply control instruction program 128repeats the determination at step 5004. When the E-mail application 130starts accessing the LU 264, the disk power supply control instructionprogram 128 instructs the disk array 200 to turn off the LU 263 thatterminated the access from the E-mail application 130 (step 5005). Thedisk power supply control instruction program 128 then determineswhether or not the remaining time is shorter than or equal to thespecified time until the scheduled time of terminating the access to theLU 264 (step 5006). When the remaining time is longer than the specifiedtime until the scheduled time of terminating the access, the disk powersupply control instruction program 128 repeats the determination at step5006. When the remaining time becomes shorter than the specified time,the disk power supply control instruction program 128 instructs the diskarray 200 to turn on the LU 265 (step 5007). The disk power supplycontrol instruction program 128 then determines whether or not theE-mail application 130 starts accessing the LU 265 (step 5008). When theE-mail application 130 does not start accessing the LU 265, the diskpower supply control instruction program 128 repeats the determinationat step 5008. When the E-mail application 130 starts accessing the LU265, the disk power supply control instruction program 128 instructs thedisk array 200 to turn off the LU 264 that terminated the access fromthe E-mail application 130 (step 5009). Finally, the disk power supplycontrol instruction program 128 determines whether or not the access tothe LU 265 terminates (step 5010). When the access does not terminate,the disk power supply control instruction program 128 repeats thedetermination at step 5010. When the access from the E-mail application130 terminates, the disk power supply control instruction program 128instructs the disk array 200 to turn off the LU 265 (step 5011). Therehas been described the operation of the disk power supply controlinstruction program 128. Like the first embodiment, the disk array 200receives a disk power supply control instruction from the computer 100.The disk array 200 references the disk management table 224 to locatethe disk device corresponding to the LU to be turned on or off and turnson or off the disk device.

It may be preferable to instruct the disk array 200 to turn on or offdisk devices corresponding to the LU based on a user input. For example,the user may use the input section 610 of the management terminal 600 toissue an instruction to the LU protection instruction program 131 so asto protect an LU against reading or writing. In this case, the diskpower supply control instruction program 128 instructs the disk powersupply control program 225 of the disk array 200 to turn off diskdevices belonging to the LU that is instructed to be protected. The usermay use the input section 610 of the management terminal 600 to issue aninstruction to the LU protection instruction program 131 so as torelease the protection of an LU against reading or writing. In thiscase, the disk power supply control instruction program 128 instructsthe disk power supply control program 225 of the disk array 200 to turnon disk devices belonging to the LU that is instructed to beunprotected.

The embodiment has been described using the E-mail application as anexample. Consequently, the flowchart in FIG. 11 shows the operation ofspecifying the sequence of LUs for writing data and sequentially turningon or off the disk devices belonging to the LU at specified times.However, the embodiment is not limited to the E-mail application and iscapable of turning on or off disk devices constituting the LU to beaccessed for reading or writing.

The embodiment can operate only disk devices reading or writing data andstop the other disk devices not reading or writing data, making itpossible to extend the disk array's operation period and decrease itspower consumption.

The disk controller 250 controls turning on or off the disk devices insynchronization with the timing when the disk array 200 receives aninstruction from the computer 100 to turn on or off the disk devices.While the disk device is turned off, the computer 200 does not accessthe disk device. This can prevent a time-out condition of accessrequests from the computer 200.

It is possible to extend the operation period and the total active timeof the disk devices constituting the disk array and decrease the diskarray's power consumption.

1. A system comprising: a disk array apparatus including first diskdevices configuring a first logical unit and second disk devicesconfiguring a second logical unit and a controller coupled to the firstdisk devices and the second disk devices; and a computer coupled to thedisk array apparatus, wherein in response to a first instruction fromthe computer, the controller starts to copy data from the first logicalunit to the second logical unit, wherein when the computer issues thefirst instruction to the disk array apparatus, the computer issues asecond instruction to request the controller to turn on the second diskdevices configuring the second logical unit, so that in response to thesecond instruction, the controller turns on the second disk devicesbefore the controller starts to copy data from the first logical unit tothe second logical unit, wherein the computer issues a third instructionto the disk array apparatus to request the controller to stop datacopying from the first logical unit to the second logical unit, whereinafter the computer receives a report of stop of the data copying fromthe first logical unit to the second logical unit, the computer issues afourth instruction to the disk array apparatus to request the controllerto turn off the second disk devices, and wherein the controller turnsoff the second disk devices in response to the fourth instruction.
 2. Asystem according to claim 1, wherein the computer issues a first commandcomprising the first instruction and the second instruction.
 3. Acomputer system according to claim 1, wherein after the data copyingfrom the first logical unit to the second logical unit stops, thecomputer executes a back up operation of data from the second logicalunit to a backup storage media.
 4. A system according to claim 2, wherewhen the controller receives the first command, the controller turns onthe second disk devices in response to the second instruction before thecontroller starts to copy data from the first logical unit to the secondlogical unit in response to the first instruction.
 5. A system accordingto claim 1, wherein an accumulated time by totaling the time duringwhich the second disk devices is turned on is recorded, and when theaccumulated time exceeds a predetermine time threshold, an alarm isissued.